Objective Against the backdrop of increasing urban stormwater flood risks and the national promotion of “dual-use” public infrastructure, exploring the multifunctional composite utilization and spatial efficiency improvement pathways for flood storage and detention areas is crucial. This paper aims to develop a spatial evaluation method for assessing both flood detention and storage, and recreation potential, quantitatively reveal their trade-offs/synergies, and provide a scientific basis for spatial planning and precise configuration of flood storage and detention areas under the “dual-use” concept.

Method Taking the Beijing’s Second Greenbelt as study area, this research coupled multi-criteria decision analysis (MCDA) with geographic information systems (GIS) to construct a dual-potential evaluation indicator system for flood detention and storage, and recreation. The entropy weight method was used for objective weighting, and GIS-based spatial weighted overlay analysis was applied to characterize the spatial distributions of the two types of potential. Subsequently, spatial autocorrelation analysis was employed to quantitatively identify the spatial trade-off and synergy patterns between them.

Result (1) Flood detention and storage potential overall showed a “high in northwest, southwest, southeast; low in northeast” pattern, with high-potential areas mainly distributing in the western hills, southwestern and eastern low-lying river network zones. (2) Recreation potential showed a structure of “high in the center, low in the periphery, with prominent local patches”. High-potential areas were concentrated in the western mountains, northeastern wetlands, and key nodes in the south. (3) Spatially, the relationship between the two functions was predominantly characterized by trade-offs, with limited synergistic areas. Specifically, high flood detention and storage-high recreation synergy clusters were found in the western piedmont and eastern wetlands; high flood detention and storage-low recreation trade-off areas were concentrated in the low-lying river networks of the southwestern and southeastern area; low flood detention and storage-high recreation trade-off areas were primarily located in urbanized areas near the center; low flood detention and storage-low recreation clusters were scattered around built-up land and major transportation corridors.

Conclusion This study developed a comprehensive evaluation indicator system for flood detention and storage and recreation potential suitable for the “dual-use” scenario, clarified their trade-off/synergy relationship and spatial differentiation, and accordingly proposed differentiated optimization strategies tailored to each functional zone. The results provide a theoretical framework and decision-support for spatial identification, zoning management, and synergistic optimization of “dual-use” flood detention and storage areas.